Distinguished iNANO Lecture

Protein cages as building blocks for nanomaterials

Professor Mauri A. Kostiainen Biohybrid Materials Group, Department of Bioproducts and Biosystems, Aalto University, Espoo, Finland

Atomic crystal structure affects the electromagnetic and thermal properties of common matter. Similarly, the nanoscale structure controls the properties of higher length-scale metamaterials, for example nanoparticle superlattices and photonic crystals. We have investigated the self-assembly and characterization of binary solids that consist of crystalline arrays of protein cages and 2) other functional units.¹
The extremely well-defined structure of protein cages (e.g. viruses and ferritins) facilitates the construction of co-crystals with large domain sizes. The use of a second functional unit allows highly selective pre- or post-functionalization with different types of functional units, such as supramolecular hosts^2,3 , enzymes⁴ and plasmonic nanoparticles.⁵
Our systematic approach identifies the key parameters for the assembly process (ionic strength, electrolyte valence, pH) and highlights the effect of the size and aspect ratio of the virus particles, which ultimately control the crystal structure and lattice constant. Protein-based mesoporous materials⁶ , nanoscale multicompartments and metamaterials are all applications that require such high degree of structural control. We have also shown that native virus particles can be disassembled and the isolated virus capsid proteins can be reassembled on the surface of DNA origami nanostructures.⁷
Using a “scaffolded artificial genome” (origami) with particular size and 3D shape, offers an interesting way to direct the capsid into nanoshapes that differ from the strictly defined T = n structures, commonly observed with native viruses. Protein encapsulation could also enhance stability and immunocompatibility⁸ of functional DNA origami devices.^9,10

References

1. Kostiainen, M. A. et al. Electrostatic assembly of binary nanoparticle superlattices using protein cages. Nat. Nanotech. 8, 52–56 (2013).
2. Beyeh, N. K. et al. Crystalline cyclophane–protein cage frameworks. ACS Nano 12, 8029–8036 (2018).
3. Shaukat, A., Anaya‐Plaza, E., Beyeh, N. K. & Kostiainen, M. A. Simultaneous Organic and Inorganic Host‐Guest Chemistry within Pillararene‐Protein Cage Frameworks. Chem. – A Eur. J. 28, e202104341 (2022).
4. Liljeström, V., Mikkilä, J. & Kostiainen, M. A. Self-assembly and modular functionalization of three-dimensional crystals from oppositely charged proteins. Nat. Commun.
5. 4445 (2014). 5. Liljeström, V. et al. Cooperative colloidal self-assembly of metal-protein superlattice wires. Nat. Commun. 8, 671 (2017).
6. Korpi, A. & Kostiainen, M. A. Sol‐Gel Synthesis of Mesoporous Silica Using a Protein Crystal Template. ChemNanoMat e202100458 (2022). doi:10.1002/cnma.202100458
7. Mikkilä, J. et al. Virus-encapsulated DNA origami nanostructures for cellular delivery. Nano Lett. 14, 2196– 2200 (2014).
8. Auvinen, H. et al. Protein Coating of DNA Nanostructures for Enhanced Stability and Immunocompatibility. Adv. Healthc. Mater. 6, 1700692 (2017).
9. Ijäs, H., Hakaste, I., Shen, B., Kostiainen, M. A. & Linko, V. Reconfigurable DNA origami nanocapsule for pHcontrolled encapsulation and display of cargo. ACS Nano 13, 5959–5967 (2019).
10. Julin, S., Nonappa, Shen, B., Linko, V. & Kostiainen, M. A. DNA‐origami‐templated growth of multilamellar lipid assemblies. Angew. Chem. Int. Ed. 60, 827–833 (2021).